Extracting composition and strain profile of semiconductor quantum dots with grazing incidence x-ray diffraction measurements

Since the discovery of narrow photoluminescence (PL) lines of InAs single quantum dots grown epitaxially on GaAs surfaces, an enormous amount of work has been carried out on these nanostructures for the development of optoelectronic devices such as lasers, quantum dot infrared photo-detectors, intermediate band solar cells and single-photon sources. The prime challenge in this field is to determine the growth parameters to obtain predictable composition and strain profiles within a quantum dot (QD) and size-distribution of QD so that optoelectronic properties of these quantum structures can be tuned with fundamental physics calculations. It has been pointed out recently that the intermixing within the self-assembled QD strongly influences intensity distribution and polarization of emitted photons as the confinement length of the carriers depend mainly upon the composition and strain profiles within a QD and not just on their size. We shall illustrate the usefulness of grazing
incidence x-ray diffraction techniques in extracting these profiles to improve our understanding in structure-property relationship of these quantum materials.